Full text of "USPTO Patents Application 10687850"

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PCX

WORLD INTELLECTUAL PROPERTY ORGANIZATION
International Bureau

INTERNATIONAL APPLICATION PUBUSHED UNDER THE PATENT COOPERATION TREATY (PCT)

(51) International Patent Classification :

Ci2Q 1/00, GOIN 35/00, 27/30, 27/327

(U) International Publication Number: WO 00/28068

(43) International Publication Date: 18 May 2000 (18.05.00)

(21) International Application Number: PCT/GB99/03764

(22) International fHing Date: 1 1 November 1999 (1 1 .1 1.99)

(30) Priority Data:
9824627.5

1 1 November 1998 (1 1.1 1.98) GB

(71) AppUcant (for all designated States except US): CAMBRIDGE

SENSORS LIMITED [GB/GB]; Downhams House, Down-
hams Lane, Cambridge CB4 IXT (GB).

(72) Inventors; and

(75) Inventors/Applicants (for US only): YON HIN, Bemadette
[GB/GB]; Cambridge Sensors Limited, Downhams House.
Downhams Lane, Cambridge CB4 IXT (GB). MCCANN,
James [GB/GB]; Cambridge Sensors Limited, Downhams
House, Downhams Lane. Cambridge CB4 IXT (GB).
BLAIR, Neil [GB/GB]; 122 Limes Road, Hardwick.
Cambridge CB3 7XU (GB), COX, Loma, Jean [GB/GB];
Cambridge Sensors Limited, Downhams House, Downhams
Lane. Cambridge CB4 IXT (GB).

(74) Agent: GILL JENNINGS & EVERY; Broadgate House, 7
Eldon Street, London EC2M 7LH (GB).

(81) Designated States: AE. AL. AM. AT. AU, AZ, BA, BB. BG,
BR. BY. CA. CH. CN. CR, CU, CZ, DE. DK. DM, EE,
ES, FI. GB. CD, GE, GH, GM, HR, HU. ID, IL, IN, IS, JP.
KE, KG, KP, KR. KZ. LC, LK, LR. LS. LT, LU, LV. MA,
MD, MG. MK. MN. MW. MX, NO, NZ, PL, FT, RO, RU,
' SD. SB, S(3, SI, SK. SL, TJ, TM, TR, TT, TZ. UA, UG,
US, UZ. VN, YU, ZA, ZW, ARIPO patent (GH, GM, KE,
LS. MW. SD. SL, SZ, TZ, UG, ZW), Eurasian patent (AM,
AZ. BY, KG, KZ. MD, RU. TJ. TM), European patent (AT,
BE. CH, CY, DE, DK, ES. FI. FR, GB, GR, IE, IT. LU,
MC. NL. FT. SE). QAPI patent (BF, BJ, CF, CG, CI, CM,
GA, GN, GW, ML, MR, NE, SN. TD. TG).

Published

With international search report.

(54) Title: ELECTRODE STRIPS FOR TESTING SMALL VOLUMES
(57) Abstract

A test strip comprising a support carries ah active electrode and a counterelectrode, and a layer of material within which a small
volume of liquid to be tested can be distributed and provide contact between the electrodes, and wherein an analyte-^eciftc reagent is
coated on tfie material. The layer of material can conveniently be provided in the fonn of a tape from which sections can be. cut or used
sequentially. . '

FOR THE PURPOSES OF INFORMATION ONLY

Codes used to identify States party to the PCT on the front pages of pamphlets publishing International applications under the PCT.

Albania

Spain

Lesotho

Slovenia

Armenia

Finland

Lithuania

Slovakia

Austria

Prance

Luxembourg

Senegal

Australia

Gabon

Latvia

Swauland

Azertraijan

United Kingdom

Monaco

Chad

Bosnia and Heiz^ovina

Georgia

Republic of Moldova

Togo

Barbados

Gil

Ghana

Madagascar

Tajikistan

Belgium

Guinea

The former Yugoslav

Turkmenistan

Buridna Faso

Greece

Republic of Macedonia

Turkey

Bulgaria

Hungary

Mali

Trinidad and Tobago

Benin

Ireland

Mongolia

Ukraine

Brazil

Israel

Mauritania

Uganda

Belanis

Iceland

Malawi

United States of America

Canada

Italy

Mexico

Uzbekistan

Central African Republic

Japan

Niger

Viet Nam

Congo

Kenya

Netherlands

Yugoslavia

Switzerland

Kyigyzstan

Norway

Zimbabwe

C6cc d'lvoirc

Democratic People's

New Zealand

Camenxm

Republic of Korea

Poland

China

Republic of Korea

Portugal

Cuba

Kazakstan

Romania

Czech Republic

Saint Lucia

Russian Federation

Germany

Liechtenstein

Sudan

Dcnmait

Sri Lanka

Sweden

Estonia

Liberia

Singapore

wo 00/28068

PCT/GB99/03764

Electrode Strips for Testing Small Volumes

Field of the Invention

This invention relates to electrode strips for testing small volumes of,
say, whole blood.
5 Background of the Invention

Diabetes is one of the most common endocrine conditions. Sufferers
must monitor their blood glucose level frequently. This is usually achieved by
the use of small test strips which detect blood glucose.

Problems commonly experienced by users of these test strips are an

10 inadequate amount of blood on the test strip and bad placement of the blood
on the test strip. A number of devices have addressed this problem by using
sample chambers that fill by capillary action. The sample is retained in close
proximity to the electrodes which facilitate the measurement of the specific
analyte in the sample; see EP-A-0170375 and US-A-5141868.

15 Such known devices comprise electrodes deposited on a non-conducting

substrate, coated with a reagent system specific for the analyte of interest and
housed within a cavity whose dimensions are sufficiently small to allow
introduction of a sample, ag. 2.5-3 pL in volume, by capillary action. The
extent to vWiich these devices can be miniaturized is limited by both the

20 manufacturing tolerances and the signal-to-noise ratio achievable with their
chemistry.

US-5820551 discloses a test strip comprising a support carrying a
working electrode and a counter electrode, and an enzyme and a mediator that
are coated on the active electrode. A drop of whole blood can provide a
25 conducting path between the electrodes, and the concentration of glucose in
the blood can be detemnined. The active electrode is exposed to a whole blood
sample without an intervening membrane or other whole blood filter.

WO-A-98/55856 (published after the priority date claimed for this
Application) discloses an analyte-specific reagent coated on the conductive
30 layer, and a monofilament mesh laid over the reagent and the reference
electrode. A sample application area is provided at one edge of the mesh.

wo 00/28068

PCT/GB99/03764

Summary of the Invention

According to a first aspect of tlie present invention, a test strip comprises
a support carrying an active electrode and a counterelectrode, and a layer of
a material within which a small volume of liquid to be tested can be distributed
5 and provide contact between the electrodes, and wherein an analyte-specific
reagent such as one component of a redox reaction, e.g. an enzyme, co-factor
or mediator, is coated on the material. In particular, the invention provides a
test strip for blood glucose, in which the sample requirement is very small, and
efficient reaction l^inetics are achieved by the application of the reagents in a

10 novel manner.

The reagent-coated material may itself be in tape form. According to a
second aspect of the invention, a flexible tape is of a material within which
liquid can be distributed and on which are coated discrete areas of at least one
component of a redox reaction.

15 Description of the Invention

In accordance with this invention, any one or more of the components of
a redox reaction, e.g. an enzyme such as glucose oxidase or glucose
dehydrogenase, a co-factor and a mediator may be applied to a mesh or
membrane which is placed overthe device. For the purpose of illustration only,

20 the invention may be described with reference to an enzyme-coated mesh.
Whichever component or components are used, when the sample is added,
they are solubilised quickly and form an efficient reaction medium that can
provide contact between the separate electrodes of the test strip. In this
manner, the reaction will proceed rapidly and without diffusion baniers. This

25 reaction configuration is particularly indicated in cases where the sample
volume is tow, the sample is viscous (such as with whole blood) and a rapid

reaction is required.

In a typical embodiment of the Invention, the sensor test strip consists
of two electrodes, one of which acts as a working electrode and another which
3 0 acts as a counter, reference electrode. The end of the working electrode that
is exposed to the sample has a mediator In intimate contact with it. The test
strip effectively provides a reaction chamber defined by these two electrodes

wo 00/28068

PCT/GB99/03764

and an additional sheet, overlying the electrodes, which has been pre-coated
with the redox enzyme and any necessary co-factor for that enzyme. The
reaction chamber may also comprise further sheets of material and/or wetting
agents, e.g. a surfactant, or cell-lysing materials (which may be placed in any
5 one of the overlying sheets). In this manner, the active enzyme is not coated
onto the conductor which forms the working electrode but is provided in a
separate layer above it which, in turn, effectivelyfonns the solution phase of the
reaction chamber. When combined v^rith lateral flow, conditions are created that
approach efficient mixing in a stin-ed reaction chamber.
Lo In an example of the invention, a silver chloride/silver reference/counter

electrode is located adjacent to a carbon electrode. Typically, for this purpose,
a pair of printed carbon electrodes is printed on a non-conducting substrate,
and then silver/silver chloride is printed on one of the carbon electrodes to
function as the reference/counter electrode. A non-conducting ink is printed
15 over the carbon electrodes and the substrate, in order to define a portion of
each electrode as a contact pad for insertion into a meter and another portion
on each electrode away from the contact pad as the sensing area where the
sample is received.

A mediator for the enzyme cofactor NADH is then prepared and
20 deposited onto the electrode from aqueous solution by pipetting. Afurther layer
containing NAD is then deposited onto the working electrode.

■ A monofilament mesh material Is coated with a surfactant and then with
a solution containing glucose dehydrogenase via pipetting, ink jet-coating or
dip-coating, and is placed over the two electrodes to form a reaction chamber.
25 This reaction chamber may be defined further by additional printing, or by the
use of a top layer to form an edge fill cavity. For example, a second non-
conducting ink printed on top of the mesh material, and then a cover tape is
applied on top of the mesh in such a way as to leave an extended area of the
mesh exposed for sample application.
30 The device allows the application of a small volume of sample (typically

1 |jL or less) to the mesh extension. This is followed by flooding of the device

wo 00/28068 PCT/GB99/03764

sensing area with sample, bringing it into intimate contact witli Vne measuring,
electrodes.

Devices having an edge fill are described in WO-A-98/55856. They can
be simply adapted, in accordance with the present/invention. In particular.
5 reference may be made to Fig. 1 in yVO-A-98/55856; components of this
invention are the support (1 ), electrodes (2/3), mesh material (6) and tape (7);
in addition, reagent is provided on the mesh material Such a device can work
by application at its edge, to a sample. This is particularly valuable in cases
where it is difficult to extract the sample. Other configurations will be evident
10 to one skilled in the art, including combinations of one or more of the cofactor,
mediator or the enzyme coated onto the overlying mesh or membrane sheets.
The choice of combination may on the reaction kinetics of the various
compounds.

In another embodiment of the device, the enzyme or the mediator is

15 coated on the sheet, the co-factor and the other of the mediator or the enzyme
are coated onto the working electrode directly, and the sheet is capable of
filtering the whole blood such that the active electrode sees a sample which is
effectively free of whole blood cells. In this case, the haematocrit dependency
of the result is substantially reduced. In this manner, the cell-filtering function

20 of a selected membrane may be combined with the rapid kinetics of having the
some or all of the active elements of the reaction (the enzyme, mediator and the
co-factor) in the membrane, to produce a highly effective device.

In summary, according to the present invention, a device is constructed
by depositing one or more of the reagents required for the quantitation of an

2 5 analyte as a single or multiple layers on a fine mesh material or membrane; the
deposited areas are of dimensions small enough to wet with a very small
sample volume. The mesh or membrane can be used in both colorimetric and
electrochemical devices.

A characteristic of this invention is that a reagent is applied precisely

30 onto a target area on a woven material such as polyester or nylon or other
porous membrane, in use, this provides rapid solubilisation of the reagents in
the presence of the sample. The reagent or reagents can be applied in a

wo 00/28068

PCT/GB99/03764

5 •

number of different methods that result in the deposition of a known volume at
a precise location and in a well-defined foot-print. These include the use of
dispensing equipment such as a piston pump, syringe pump or on-demand ink-
jet printer.

5 In a further embodiment, a flexible tape containing one or more reagents

may be laminated to another flexible tape on which is printed a series of
electrodes. Instead of cutting out individual sensors, the laminate (comprising
a row or series of sensors) may be used sequentially, e.g. on being dispensed
from a suitable dispenser. For this purpose, whether or not as a laminate, a

10 tape of the invention may be provided as a roll, and stored in sealed cassettes
which may also contain desiccant. in use, the cassette may be inserted into a
automatic dispenser from which the tape is wound out automatically by an
indexing mechanism to reveal sequentially the discrete sensors. The action of
this instalment is therefore analogous to the action of a film in a camera In this

15 embodiment, the tape may also contain a red blood cell-lysing reagent such as
saponin, in order to reduce the effect of haematocrit and haemoglobin in a
whole blood sample. The tape may be further protected from moisture by being
covered with a peelable film (e.g. of aluminium) that is automatically peeled off
when the tape is dispensed from the cassette. When the sample is applied to

20 the sensor, the amount of analyte of interest in the sample may be determined
electrochemically. Such determination can be conducted by known methods.

The following Example Illustrates the invention.
Example

A conductive ink material is printed onto a non-conducting polyester
25 sheet material by a screen-printing process. The conductive ink material
consists of a mixture of graphite and carbon particles and a polymer binder in
an organic solvent. After deposition of the conductive ink, solvents are
removed in a forced air oven. A silver/silver chloride reference/counter
electrode is printed onto one of each pair of printed cariaon electrodes followed
30 by a non-conducting ink layer to define the contact pads and the sensor area.

A mediator such as Meldola Blue, Nile Blue or other suitable dye and the .
enzyme co-factor nicotinamide adenine dinucleotide (NAD) are deposited onto

wo 00/28068

PCT/GB99/03764

the carbon electrode. Alternatively, the NAD is applied separately over the
mediator from an aqueous ink.

The enzyme glucose dehydrogenase is deposited as uniform spots on
a monofilament polyester mesh tape. This is achieved as follows:
5 (a) in a contact mode, where a drop formed at a dispenser lip in

close proximity to the mesh is allowed to be transferred to the
mesh by touching off the drop onto the mesh surface; or
(b) in a non-contact mode, where a drop formed by an ink-jet print-
head or other orifice above the mesh is dropped onto the mesh
10 from a distance under conditions which do not cause it to

penetrate the mesh.
Upon drying, the spots spread to cover an area defined partly by the
characteristics of the mesh weave and partly by the application conditions.
Typically the areas covered by a 500 nL drop is 1.3 x 1 .2 mm. The mesh tape
15 is allowed to dry at room temperature.

The enzyme-modified mesh tape is then laminated onto the modified
sheet of devices and secured further by a non-conducting print. Finally, a cover
tape is laminated on tope of the mesh. The sheets of devices are disc cut into
individual devices. In an alternative device format, the laminated sheets are
2 0 wound and included in a cassette type unit, allowing a single device to be used
by a wind-on mechanism similar to a camera film-winding system.

wo 00/28068

PCT/GB99/03764

CLAIMS

1. A test strip comprising a support carrying an active electrode and a
countereiectrode. and a layer of material within which a small volume of liquid
to be tested can be distributed and provide contact between the electrodes, and

5 wherein an analyte-specific reagent is-coated on the material.

2. A test strip according to claim 1, wherein the reagent is at least one
component of a redox reaction, e.g. one or more of an enzyme, a mediator
and/or co-factor for the enzyme.

3. A test strip according to claim 2. whereih the at least one component
10 comprises the enzyme.

4. A test strip according to claim 2 or claim 3, wherein the enzyme is
glucose oxidase or glucose dehydrogenase.

5. A test strip according to any preceding claim, wherein the material is a
monofilament mesh or membrane.

15 6. A flexible tape of a material within whicti liquid can be distributed and on
which are coated discrete areas of at least one component of a redox reaction.

7. A flexible tape according to claim 6, wherein the material is a
monofilament mesh or membrane.

8. A container containing a wound tape according to claim 6 or claim 7.
20 9. A container according to claim 8 also comprising automatic dispensing

means.

10., A method for testing a liquid for the presence of an analyte. which
comprises contacting the liquid with a test strip according to any of claims 1 to
5, and detecting the current.
25 11. A method according to claim 10, wherein the liquid is blood and the
analyte is glucose.

INTERNATIONAL SEARCH REPORT

M ionHAwMionlto

PCT/GB 99/03764

iprr*c!isr/sr'"'"GofN35/oo 601N27/30 G01N27/327

ABCOidho to trtamailon^ Patent aasstficaflon (IPOof tobottinatfonri

and IPC

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IPC 7 C12Q GOIN

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BaoUonlo data baseoonMM during the htemattofwieeeroh (name of database and, where pmoHoaLaeerahtenm used)

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rMflVii A to dafcii Nql

UO 97 02487 A (BOEHRINGER NANNHEIH CORP)
23 January 1997 (1997-01-23)
page 1, line 33 -page 8, line 28; figure
1; table 1

\!S 5 169 600 A (ISHIZAKA HIDEO
8 December 1992 (1992-12-08)
column 8, line 15-34

ET AL)

US 5 779 867 A (SHIEH PAUL)
14 July 1998 (1998-07-14)
coTunm 4, line 14-21; claims 1-4
abstract

1-5,10,
11

7-9
1

7-9

1-5,10,
11

-/-

Further docunente are l«ted In the oonthuaUon of i>ox C.

PsMl (ainlly memtieiB are Medfei aiiieXi

* Special oatagoifee of dted doounente :

*A" docunentdelMiothegener^et&teofthe aitwNchlanot

ooneldered tobe ol paitlouiarielevanoe
"E* esiDer doounent but pufalihedcn or after tfw kttemaflonal

fUnQdste

V doounefrtwfkhfimYtfvo^

vvhich ie olted to ewabiMi the plisllcailon date of another
ollaflon or dheripeoial reeeon (as apecffled)

'V iloou rayt tefe nInQ to anotal cflagtoiure, uae, eMIttonor
other means

"P" doounantptisfafiedprlortothekitefnallonsJ flbng dale but
later than the priority date dalmed

T loterdooumentpiiilMiedafterthe bitematlonal Ubig date
or priority date and not hoonfldviMi the apptatfonfaut
dted to uidentand the prhciito or theory uideriylnothe

InvsnHan

"X" doounentotpai11cdarfelevanoe;theelalmed bwertfon
cmot be oonaldeied novel or cannot be oonsMeied to
Involve en InvetHtve step when the dooinentle tahen alone

■Y" doamertf of parikKiarielevanoe; the claimed Irwertian
cmot be consldeied to Involve en h)venllve atepwhenthe
docunentle combined wNh one or more other suchdoou-
menta^euohcomfahatianbebiQ obvious to a peraonddled
ki the art.

"&* document member of the eamepetertfamly

Date of the actual oompicdon of the hitem&tfonal aeetch

11 February 2000

Date of maflng of the bttemadlonal eeeioh report

24/02/2000

Name and maOna addiesa of the ISA

Etnpean Patert Offloe. P.a 5818 Patendasna

NL-22aOHVRt)Mi(|c

Tel. (431-70) 340-2040. Tx. 31 851 epo rl.

Fas (431-70) 340-3018

Rsm PCTA8AS10 (Mdond ttm^ (J^ lOOS)

AulhortMd ofBoer

Brison. 0

page 1 of 2

INTERNATIONAL SEARCH REPORT

PCT/GB 99/03764

CL(OonttilMtton) OOCUUEKTS CONStDERED TO BE RELEVANT

RetovanttodfllnNa

A.P

US S 798 031 A (CHARLTON STEVEN C ET AL)

25 August 1998 (1998-08-25)

abstract

column 5, line 22-25

US 5 628 890 A (CARTER NIGEL F ET AL)

13 May 1997 (1997-05-13)

column 3, line 41 -column 4, line 10

abstract

EP 0 230 472 A (MATSUSHITA ELECTRIC INO CO
LTD) 5 August 1987 (1987-08-05)
page 7, line 14-25

EP 0 593 096 A (HEDISENSE INC)

20 April 1994 (1994-04-20)

page 6, line 57 -page 7, line 3; figure 3
page 2, line 28-50

US 4 218 421 A (HACK JOHN C JR ET AL)

19 August 1980 (1980-08-19)

column 2, line 43 -column 4, line 53

US 5 679 311 A (HARHIS HERBERT ET AL)

21 October 1997 (1997-10-21)
abstract; figure 2A

UO 99 13100 A (ABBOn LAB)
18 March 1999 (1999-03-18)
abstract; figure 1

1-5.10,
11

6-8

1-5,10,
11

6-9
1

6-9

&-8

page 2 of 2

INTERNATIONAL SEARCH REPORT

PCT/6B 99/03764

PtMcBllen

Patent famly

PiMcaflon

cftodin aoafch report

date

yO 9702487

23-01-1997

5762770 A

09-06-1998

712527 B

11-11-1999

6345196 A

05-02-1997

2224308 A

23-01-1997

0874984 A

04-11-1998

08-12-1992

1020454 A

24-01-1989

2119175 C

06-12-1996

8020453 B

04-03-1996

1020455 A

24-01-1989

2119176 C

06-12-1996

8020454 B

04-03-1996

1080865 A

27-03-1989

WW *^ww

1080866 A

27-03-1989

3853700 D

08-06-1995

3853700 T

WW%rv# WV 1

07-09-1995

0299519 A

Wb99^A7 r*

18-01-1989

5122343 A

16-06-1992

AW WW A^^fc

US 5779867

14-07-1998

5522977 A

04-06-1996

5645710 A

08-07-1997

US 5798031

25-08-1998

6482198 A

12-11-1998

2236132 A

12-11-1998

0878708 A

18-11-1998

JP
VI

10318971 A

04-12-1998

329793 A

25-11-1998

lie CA900Qfl

13-05-1997

2159553 A

30-03-1997

9222411 A

26-08-1997

05-08-1987

2624236 B

25-06-1997

62232554 A

13-10-1987

6048256 B

22-06-1994

61294351 A

25-12-1986

1915067 C

23-03-1995

6040088 B

WV^VVWW w

25-05-1994

62108145 A

19-05-1987

1949170 C

10-07-1995

6076984 B

W » www" 1/

28-09-1994

62108146 A

19-05-1987

1915084 C

23-03-1995

6040089 B

25-05-1994

62137559 A

20-06-1987

3687646 A

vwWr V~ w ft

11-03-1993

liW

8607632 A

31-12-1986

w«

4897173 A

30-01-1990

5185256 A

09-02-1993

EP 0593096

20-04-1994

622196 B

02-04-1992

3822089 A

01-02-1990

1313397 A

02-02-1993

0352138 A

24-01-1990

2112752 A

25-04-1990

5126034 A

30-06-1992

US 4218421

. 19-08-1980

NONE

Fomi PGT/l8Aft10 (pBtmt fsmly miO <*Uy 1 M2)

page 1 of 2

INTERNATIONAL SEARCH REPORT

PCT/6B 99/03764

Patort document
cSsd In 888fch report

PiMcalfon
(Sato

Patantfamly
nwinbM(a)

PiMofloh
dais

us 5679311 A

21-10-199/

4326339 A

0637749 A

08-02-1995

2610109 B

14-05-1997

7077528 A

20-03-1995

5609823 A

11-03-1997

WO 9913100 A

18-03-1999

9129798 A

29-03-1999

Fm PCT/BM»0 (POM IMy «nrai« (lUy lOSQ

page 2 of 2

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Full text of "USPTO Patents Application 10687850"

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